# Neonatal Thermoregulation and Hypothermia

> Neonatal thermoregulation and hypothermia for NEET-PG Paediatrics covering heat loss routes, brown fat, cold stress and the warm chain used in newborn care.

- Canonical URL: https://prepelephant.com/topics/neet-pg/paediatrics/neonatal-thermoregulation-and-hypothermia
- Exam / course: NEET-PG · Subject: Paediatrics
- Publisher: PrepElephant (https://prepelephant.com) — Prepared and reviewed by the PrepElephant Academic Review Team
- First published: 2026-10-14
- Last updated: 2026-10-14
- Reference basis: Nelson Textbook of Pediatrics; IAP Textbook of Pediatrics; Essential Newborn Care guidance of the Indian national newborn programme
- How to cite: "Neonatal Thermoregulation and Hypothermia", PrepElephant, https://prepelephant.com/topics/neet-pg/paediatrics/neonatal-thermoregulation-and-hypothermia

## Direct answer

Neonatal thermoregulation is the newborn's ability to hold a stable body temperature, and it is weak because of a large surface area for weight, thin skin, little fat and poor shivering. Heat is produced mainly by non-shivering thermogenesis in brown adipose tissue. A temperature below 36.5 degrees Celsius is abnormal (WHO: 36.0 to 36.4 is cold stress and below 36.0 is hypothermia), and sustained hypothermia drives hypoglycaemia, acidosis and respiratory failure, so prevention through the warm chain is central to care.

## What you must remember

- **Normal range:** axillary temperature of about 36.5 to 37.5 degrees Celsius, with the core temperature usually a little higher.
- **Heat loss routes:** conduction to cold surfaces, convection from draughts, radiation to cold walls and evaporation from wet skin, which is the largest threat right after birth.
- **Heat production:** brown adipose tissue, located mainly between the scapulae and around the great vessels, produces heat through non-shivering thermogenesis.
- **Cold stress:** a fall below 36.5 degrees Celsius (WHO cold stress band 36.0 to 36.4) that the baby compensates for by increasing oxygen consumption and glucose use.
- **Consequences:** hypoglycaemia, metabolic acidosis, respiratory distress, feeding intolerance and increased risk of sepsis and intraventricular haemorrhage in preterm infants.
- **Prevention:** immediate drying, skin-to-skin contact, a warm room, a cap, delayed first bath and transport in a warmed incubator.
- **Preterm specifics:** a very preterm baby may be wrapped in plastic without drying, because the skin is permeable and evaporative loss is severe.

## Heat loss and the warm chain

Hypothermia is best understood by matching each heat loss route to the step of the warm chain that blocks it. The table pairs them, in the order that examiners tend to test them, and each route has a simple bedside fix.

| Heat loss route | Newborn example | Warm chain step |
|---|---|---|
| Evaporation | Wet skin after birth | Immediate drying and a warm towel |
| Convection | Draughts and open cots | Warm room and avoid fans |
| Conduction | Cold scales and cold tables | Pre-warmed surfaces and a cloth layer |
| Radiation | Cold walls and windows | Skin-to-skin contact and a cap |

Evaporation is the largest loss in the first minutes, which is why drying comes first in the sequence. Brown fat thermogenesis burns glucose and oxygen, so a cold baby quickly becomes hypoglycaemic and acidotic, and prevention is therefore safer and cheaper than rescue. In practice no single intervention closes every route, so the team combines several steps at once, especially for a low birth weight baby.

## Where the exam tries to catch you

Thermoregulation questions usually test the mechanism behind each intervention and the reason for each delay.

- **Trap:** believing a newborn shivers to keep warm. — **Correct:** newborns rely on non-shivering thermogenesis from brown fat, because shivering is poorly developed.
- **Trap:** giving the first bath soon after birth to clean the baby. — **Correct:** the first bath is delayed, usually for at least 24 hours, to prevent heat loss and infection.
- **Trap:** drying a very preterm baby before wrapping. — **Correct:** a preterm baby below about 32 weeks is wrapped in plastic without drying, because evaporative loss through thin skin is severe.

## Frequently asked questions

### Why do newborns lose heat so quickly?

Newborns have a large surface area for their weight, thin skin and little subcutaneous fat, which together speed heat loss. Their limited shivering capacity means they depend mainly on brown fat for heat production.

### What is the most important route of heat loss immediately after birth?

Evaporation from wet skin is the most important route of heat loss immediately after birth. Drying the newborn promptly and covering the head reduces this loss.

### Which intervention is most effective for preventing hypothermia in a newborn?

Skin-to-skin contact with the mother is one of the most effective ways to prevent hypothermia in a newborn. It provides a warm, stable environment that the baby cannot easily achieve alone.

### Why is hypothermia dangerous for a newborn baby?

Hypothermia in a newborn baby increases oxygen and glucose use, causing hypoglycaemia, metabolic acidosis and respiratory distress. It also raises the risk of sepsis and, in preterm infants, intraventricular haemorrhage.